JPH04110959A - Plural color image forming device - Google Patents

Abstract

PURPOSE:To form the image of plural colors and to miniaturize the device by electrifying uniformly the surface of an electrostatic latent image carrier and forming an electrostatic latent image of plural potential levels on the surface of the electrostatic latent image carrier by one light source, developing this electrostatic laten image by a different color toner electrified to different polarity, and subsequently, electrifying this different color toner to the same polarity, and transferring it to an image receiving material. CONSTITUTION:By a first electrifying means 14, the electrostatic latent image carrier surface 12A is electrified uniformly, and on this electrostatic latent image carrier surface 12A, an electrostatic latent image consisting of plural potential levels is formed by changing the exposure quantity of a light source 16 by one light source 16. Subse quently, this electrostatic latent image is developed by allowing a different color toner electrified to different polarity to adhere in a developing means 18, and by a second electrifying means 20, the different color toner on the electrostatic latent image carrier is electrified to the same polarity. Thereafter, the different color toner image on the electrostatic latent image carrier 12 is transferred to an image receiving material. In such a way, an image consisting of plural colors can be formed by one light source, and also, since the number of light sources is one, the device can be miniaturized.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a multi-color image forming apparatus that forms images of multiple colors.

[Conventional technology]

A multi-color image forming device electrostatically applies black or other color toner to an electrostatic latent image corresponding to an image signal formed on the surface of an electrostatic latent image carrier (photoreceptor) in order to obtain a visible image. This is a device that obtains a desired image by attaching it to a transfer medium such as paper, and then fixing it by pressure, heat, etc. after transferring it to a transfer medium such as paper.

- The basic configuration for obtaining a two-color image using this multi-color image forming apparatus for boat fishing is (1) Charging-Exposure-Development-Charging-Exposure→Development-Transfer constant; A schematic configuration diagram in this case is shown in FIG. As shown in FIG. 7, this process aims to achieve two-color printing by repeating the monochrome printing process twice. In other words, the first charger 70. First exposure means 7
2. Obtain, for example, a black toner image with the first developing device 74,
Two chromatic colors, for example, red toner images are obtained by the second charger 76, the second exposure means 78, and the second developer 80, and these two
A color toner image is transferred to a paper 84 by a transfer charger 82.
A two-color image is obtained by transferring the image to .

Note that the reference numeral 85 in FIG. 7 indicates an electrostatic latent image carrier;
G indicates a pre-transfer charger, 88 indicates a cleaner, 90 indicates an erase lamp, and arrow A indicates the paper 8.
4, and arrow B indicates the direction of rotation of the electrostatic latent image carrier.

However, in this two-color electrophotographic image forming apparatus, in the process of forming a second toner image (for example, a red toner image), if the previously formed first toner image (for example, a black toner image) is scraped off, There are problems such as problems such as color mixing of two color toners, and problems such as color mixing of two color toners. Furthermore, since two units each for charging, exposure, and development are arranged on the same electrostatic latent image carrier (photosensitive drum), there is also the problem that the apparatus becomes larger.

As a two-color electrophotographic image forming apparatus that improves these problems, a two-color electrophotographic image forming apparatus that obtains two colors with two rotations of a photosensitive drum is known.

In this two-color electrophotographic image forming apparatus, (2) Charging - Exposure - Development - Transfer - (Cleaning) - Charging - Exposure - Development - Transfer = (Cleaning) - Transfer (from transfer drum or transfer belt to paper) → The structure is said to be established.

In this case, a toner image is obtained by the conventional process in one rotation of the photosensitive drum, this is first transferred onto a transfer drum or transfer belt, and a second toner image is transferred onto the transfer drum or transfer belt in the second rotation. This is a method in which two-color images formed on a transfer drum or transfer belt are transferred all at once onto paper. This method has the advantage that it can be applied not only to two-color printing but also to multi-color printing, and that the apparatus can be made smaller than the apparatus (1).

However, in this two-color electrophotographic image forming apparatus, the copying speed is slow, the transfer process involves two indentations, which increases the deterioration of image quality, and the paper
There are problems such as the color position being easily misaligned.

Many of the two-color electrophotographic image forming apparatuses were developed in 1983 to solve these problems and realize simpler mechanisms.
This is disclosed in Japanese Patent No. 117266, etc., and the basic structure of a typical example thereof is shown in FIG.

In this two-color electrophotographic image forming apparatus, as shown in FIG.
The first light source 9 is located downstream in the direction of rotation of the light source 96 (direction of arrow B).
8 and a second light source 99 are provided, and the configuration is as follows: (3) charging -> first exposure -> second exposure -> mixed development - pre-transfer charging - transfer -> fixing.

That is, positive exposure and negative exposure are performed on the electrostatic latent image carrier (photosensitive drum) 96 which is positively or negatively charged in the negative direction to form three different potential levels as shown in FIG. A bias potential of approximately VO/2 is applied to this to perform positive development and negative development. This allows simultaneous development of two colors.

In this two-color electrophotographic image forming apparatus, although there is a problem that color mixing occurs due to the two-color mixed development, the apparatus can be made smaller and the process can be simplified compared to the above two apparatuses.

However, this two-color electrophotographic image forming apparatus also has one more exposure mechanism (light source) than the conventional monochrome image forming apparatus, and two light sources are arranged on the electrostatic latent image carrier, making the apparatus compact. This is a negative factor from the perspective of development.

[Problem to be solved by the invention]

The present invention has been made in consideration of the above-mentioned facts, and an object of the present invention is to obtain a multi-color image forming apparatus that can form an image consisting of a plurality of colors and that can be miniaturized.

[Means to solve the problem]

The present invention according to claim (1) includes a first charging means for uniformly charging the surface of the electrostatic latent image carrier, and a plurality of potentials applied to the surface of the electrostatic latent image carrier charged by the first charging means. A light source for forming an electrostatic latent image consisting of levels; a developing means for developing the electrostatic latent image formed by the light source by attaching different colored toners charged with different polarities; a second charging means for charging different color toners on the electrostatic latent image carrier attached to the same polarity; and a different color toner image on the electrostatic latent image carrier charged to the same polarity by the second charging means on an image receiving material. The invention is characterized in that it includes a transfer means for transferring to.

The present invention described in (2) further includes a first charging means for uniformly charging the surface of the electrostatic latent image carrier, and a first charging means for charging the image information including two color signals of the first color and the second color. a signal processing means for converting and outputting a signal that can be distinguished into a color, a second color, and a background; one light source for forming an electrostatic latent image with three potential levels corresponding to one color, a second color, and a background; a developing means for depositing and developing toners of two colors; a second charging means for charging the toners of two colors on the electrostatic latent image carrier deposited by the developing means to the same polarity; The apparatus is characterized in that it includes a transfer means for transferring the two-color toner image on the electrostatic latent image carrier charged to the same polarity by the means to an image-receiving material.

Further, the present invention described in (3) is characterized in that it includes a background potential level control means for changing the background potential level.

[Effect]

In the present invention as set forth in claim (1), the surface of the electrostatic latent image carrier is uniformly charged by the first charging means, and the exposure amount of the light source is varied by one light source on the surface of the electrostatic latent image carrier. By this, an electrostatic latent image consisting of a plurality of potential levels is formed. This amount of exposure can be changed by changing the exposure time or the intensity of light. Next, this electrostatic latent image is developed by attaching different colored toners charged to different polarities in a developing means, and the different colored toners on the electrostatic latent image carrier are charged to the same polarity by a second charging means. Thereafter, the different color toner images on the electrostatic latent image carrier, which have been charged to the same polarity by the second charging means, are transferred to the image-receiving material by the transfer means.

Therefore, an image consisting of a plurality of colors can be formed using one light source, and since there is only one light source, it is possible to downsize the apparatus.

Further, in the present invention as set forth in claim (2), the surface of the electrostatic latent image carrier is uniformly charged by the first charging means. On the other hand, the signal processing means converts image information including two-color signals of a first color and a second color into signals that can be distinguished into a first color, a second color, and a background, and outputs the signals to one light source. One light source forms an electrostatic latent image on the surface of the electrostatic latent image carrier with three potential levels corresponding to a first color, a second color, and a background by varying the exposure amount of the light source. This amount of exposure can be changed by changing the exposure time or the intensity of light. Next, this electrostatic latent image is developed by attaching two colored toners charged to different polarities in a developing means, and the two colored toners on the electrostatic latent image carrier are made to have the same polarity by the second charging means. to be charged.

Thereafter, the two-color toner image on the electrostatic latent image carrier, which has been charged to the same polarity by the second charging means, is transferred to the image-receiving material by the transfer means.

Therefore, an image consisting of two colors can be formed using one light source, and since there is only one light source, it is possible to downsize the apparatus.

Further, in the present invention as set forth in claim (3), image defects such as fogging can be prevented by changing the background potential level by the background potential level control means, and a clear two-color image can be formed. .

[Embodiments of the invention]

The first embodiment of the present invention will be described below, that is, by considering the relationship between the photoelectric characteristics of the electrostatic latent image carrier and the amount of light, two light sources can be used with one light source.
A multi-color image forming apparatus that realizes the formation of color images will be described.

As shown in FIG. 1, the basic configuration of the multi-color image forming apparatus 10 of this embodiment includes a first charging means for uniformly charging the surface 12A of the electrostatic latent image carrier (photoreceptor) 12; It is equipped with a container 14. Electrostatic latent image carrier 1 of this charger 14
A surface potential sensor 15 is provided on the downstream side in the rotational direction (direction of arrow B in FIG. 1) of 2, and is adapted to detect the potential of the electrostatic latent image carrier surface 12A after being charged in a negative manner. .

On the downstream side of the surface potential sensor 15 in the rotational direction of the electrostatic latent image carrier 12, light sources 1 and 6 are provided. A potential and a second image potential are formed.

As shown in FIG. 2, the light source 16 includes a plurality of LEDs (L, ~L
n).

As shown in FIG. 3, each LED (L, ~L) of the light source 16
n) are each connected to a drive circuit 30 as a signal processing means. This drive circuit 301 is provided with a first AND circuit 34 and a second AND circuit 36.
A first timer circuit 38 that turns on the human power signal T1 is connected to the 8-power side of the AND circuit 34, and the second A
The output side of the ND circuit 36 is connected to the human input signal Tl+T2.
A second timer circuit 40 is connected to turn on the light for a certain period of time. Further, the output side of the first timer circuit 38 and the output side of the second timer circuit 40 are respectively connected to an OR circuit 42, so that the output of the OR circuit 42 is inputted to each LED of the light source 16. It has become.

The drive circuit 30 includes a print signal generator 32 that outputs image information.
The inverted signal of the print signal A and the inverted signal of the print signal B are input to the first AND circuit 34. Also, the inverted signal of print signal A and the print signal B
is manually input to the second AND circuit 36.

The print signal generator 32 is connected to image information output means such as a scanner and a computer (not shown).

As shown in FIG. 1, a developing device 18 as a developing means is provided downstream of the light source 16 in the rotational direction of the electrostatic latent image carrier 12. It is designed to be developed by attaching polarized toner of different colors.

Further, a bias voltage changing circuit 19 is connected to the developing device 18 as a background potential level control means. This bias voltage changing circuit 19 is connected to the surface potential sensor 15, and changes the bias voltage based on the surface potential of the electrostatic latent image carrier surface 12A after −-like charging, which is input from the surface potential sensor 15. It has become.

A pre-transfer charger 20 as a second charging means is provided downstream of the developing device 18 in the rotational direction of the electrostatic latent image carrier 12, and the electrostatic latent image carrier surface 12A attached by the developing device 18 is provided with a pre-transfer charger 20 as a second charging means. The different color toners on the top are charged to the same polarity. A transfer charger 22 as a transfer means is provided downstream of the pre-transfer charger 20 in the rotation direction of the electrostatic latent image carrier 12, and the electrostatic latent image carrier surface 12A charged to the same polarity by the pre-transfer charger 20 is provided as a transfer means. The upper different color toner is transferred onto paper 24 as an image receiving material.

A fixing device (not shown) is provided on the downstream side of the sheet 24 to which the different color toner has been transferred (in the direction of arrow in FIG. 1), and the toner is transferred to the sheet 24 by heat or pressure.
It has become established.

Further, a cleaning section 26 is provided on the downstream side of the pre-transfer charger 20 in the rotational direction of the electrostatic latent image carrier 12, and is configured to remove toner from the surface 12A of the electrostatic latent image carrier after the transfer is completed. There is. An exposure device (erase lamp) 28 is provided on the downstream side of the cleaning section 26 in the rotational direction of the electrostatic latent image carrier 12, and is designed to neutralize the residual charge on the electrostatic latent image carrier 12 after cleaning. ing.

Next, the operation of this embodiment will be explained.

The electrostatic latent image carrier 12 moves clockwise in FIG.
direction). The surface 12 of this electrostatic latent image carrier 12
A is uniformly charged positively or negatively by the charger 14. In this embodiment, the following description will be made assuming that the battery is positively charged.

The uniformly charged surface 12A of the electrostatic latent image carrier 12 is exposed to positive light and negative light by the light source 16 to form positive and negative electrostatic latent images.

That is, as shown in FIG. 9, the electrostatic latent image carrier surface 12A
is charged to a voltage corresponding to VO, and the photoelectric properties of this electrostatic latent image carrier 12 (a phenomenon in which it becomes photoconductive when irradiated with light of a specific wavelength and harmonizes the charges on the surface) are as shown in FIG. 4, the image signal A (for example, black signal) and the image signal B (for example, red signal) of the print generator cause each drive circuit 3 to
0 is activated, each LED (L, ~Ln) of the light source 16
turn on and off.

That is, both the image signal A (for example, black signal) and the image signal B (for example, red signal) from the print signal generator 32 are L (
For the low) level (background case), the first AND
A signal of H()1a) level is output from the circuit 34,
The LED is turned on for a time T1 during which the surface potential becomes VO/2, and the electrostatic latent image carrier surface 12A is positively exposed.

Further, when the image signal A (for example, a black signal) from the print signal generator 32 is at H level, L level signals are output from both the first AND circuit 34 and the second AND circuit 36. The LED is not turned on and the surface potential does not change from VO.

Further, when the image signal B (for example, a red signal) from the print signal generator 32 is at H level, the second AND circuit 36 outputs an H level signal for only the time T1+T2 during which the surface potential becomes almost 0. The LED is turned on, exposing the electrostatic latent image carrier surface 12A to negative light.

As a result, the surface potential of the image signal A portion remains VO, the background portion has a surface potential of VO/2, and the surface potential of the image signal B portion becomes approximately 0.

In this way, by controlling the exposure time using one light source 1, three different potential levels shown in FIG. 9 can be realized.

The surface potential level of these three values is developed with positive and negative toners in the developer 18. In this case, as a bias voltage during development, a potential of 0/2, which corresponds to the potential level of the background portion, is applied among the three potential levels shown in FIG. Further, the negatively charged toner is reversely developed in the area where the surface potential is 0. This allows toners of different colors to be developed simultaneously.

However, the positive and negative toners may be developed using separate developing devices 18, and the present invention does not particularly relate to simultaneous development.

Next, the toners of different polarity formed on the electrostatic latent image carrier surface 18 are made to have the same charge polarity by a pre-transfer charger 20 and are transferred to a sheet 24 by a transfer charger 22. The toner on the paper 24 is fixed to the paper 24 by a heat or pressure fixing device (not shown) to obtain a desired two-color image.

On the other hand, residual toner is removed from the electrostatic latent image carrier 12 by the cleaner 26.
After the residual charges are removed by the erase lamp 28, the remaining charge is erased by the erase lamp 28, and the next image forming process is started again.

Therefore, three different surface potentials can be realized with one light source 16, miniaturization of the device and simplification of the process are achieved, resulting in significant cost effects.

Further, in this embodiment, a bias voltage changing circuit 19 is connected to the developing device 18, and the bias voltage changing circuit 19 uses the bias voltage changing circuit 19 to detect the electrostatic latent image carrier after being charged in a negative manner. The bias voltage for development is controlled based on the surface potential of surface 12A. This makes it possible to control the developing bias voltage so that it is always equal to the surface potential of the background portion, and it is possible to form an image without background fogging even if the groove boundary changes and usage conditions vary.

Further, for example, if the charge amount q (+) of the positively charged toner is twice as large as the charge amount q (-) of the negatively charged toner, the bias voltage change circuit 19 stores in advance the charge amount q (-) of the negatively charged toner. Based on the relationship q(su/q(-)=2), the background potential level and bias voltage are set to VO/3 instead of VQ/2, as shown in Figure 11. Therefore, the force F acting on the toner particles in the direction of the electrostatic latent image carrier is expressed by the following formula, and the forces acting on the positive and negative toner particles are equal.

F(+)l=12q (+)Xα・VO/3=l
2/3Xq(+)xα・VO F(-)l=lq(-)Xα-Vo ・2/3=l
2/3xq(-)xα・V.

Here, α is a coefficient when determining the electric field from the potential difference, and is usually a coefficient that depends on the distance between the electrostatic latent image carrier and the sleeve of the developing device.

Setting the bias voltage in this way is also effective for obtaining a good two-color image.

In addition, in the case of two-color printing as described above, it is necessary to change the background potential level in addition to changing the bias voltage.
Control at this time is facilitated by using only one light source.

Next, a second embodiment of the present invention will be described with reference to FIGS. 5 and 6.

As shown in FIG. 5, in this embodiment, each LED of the light source 16
The lighting of (L, ~Ln) is controlled by a control circuit 44 as a signal processing means using a microcomputer, and the control circuit 44 includes image information output means such as a scanner and a computer (not shown). is connected.

Furthermore, a program for controlling the lighting of each LED (L, to Ln) of the light source 16 is stored in advance in the memory in the control circuit 44, and is based on the image information from the image information output means and the stored program. , each LE of the light source 16
D (L, ~t, n) is lit.

Next, the lighting control of each LED (L, -Ln) of the light source 16, which is performed by an interrupt routine caused by the rise of a synchronization pulse, will be explained according to the flowchart of FIG.

First, increment the counter N (step 1
00). Next, if the image information from the image information output means is not image signal A (for example, a black signal) or image signal B (for example, a red signal), that is, if it is the background,
The Nth LED of the light source 16 is turned on for the time T1 when the surface potential becomes vO/2, and the electrostatic latent image carrier surface 12A is positively exposed (steps 102 and 104).

Next, when the image information from the image information output means is not a background, and when the image information from the image information output means is an image signal B (for example, a red signal), the time T1+T2 when the surface potential becomes almost 0 Then, the Nth LED of the light source 16 is turned on, and the electrostatic latent image carrier surface 12A is negatively exposed (steps 106 and 108).

Further, the image information from the image information output means is the image signal B
If not, that is, in the case of image signal A, the LED is not lit and the surface potential does not change from VO.

The above control is performed for N LEDs (step 110
．． 112) In synchronization with the rotation of the electrostatic latent image carrier 12, the exposure control for the next pixel line is started.

As a result, the surface potential of the image signal A portion of the electrostatic latent image carrier surface 12A remains at VO, the surface potential of the background portion becomes VO/2, and the surface potential of the image signal B portion becomes approximately 0. .

In this way, in this embodiment as well, as in the first embodiment, by controlling the exposure time using one light source,
Images consisting of colors can be formed, and the device can be made smaller.

〔Effect of the invention〕

Since the present invention has the above-described configuration, it has the excellent effect of being able to form an image consisting of a plurality of colors and miniaturizing the device.

[Brief explanation of drawings]

FIG. 1 is a schematic diagram showing main parts of a multi-color image forming apparatus according to a first embodiment of the present invention, and FIG. 2 is a schematic plan view showing a light source of a multi-color image forming apparatus according to a first embodiment of the present invention. FIG. 3 is a block diagram showing a driving circuit for the light source of the multi-color image forming apparatus according to the first embodiment of the present invention, and FIG. 4 shows lighting control of the light source of the multi-color image forming apparatus according to the first embodiment of the present invention. FIG. 5 is a block diagram showing a light source driving circuit of a multi-color image forming apparatus according to a second embodiment of the present invention;
FIG. 6 is a flowchart showing lighting control of the light source of a multi-color image forming apparatus according to a second embodiment of the present invention, FIG. 7 is a schematic diagram showing main parts of a conventional multi-color image forming apparatus, and FIG. 9 is a graph showing the relationship between the print signal and the potential, and FIG. 10 is a graph showing the relationship between the exposure time potential of the electrostatic latent image carrier. , FIG. 11 is a graph showing the relationship between print signal and potential. DESCRIPTION OF SYMBOLS 10... Multi-color image forming device, 12... Electrostatic latent image carrier, 14... Charger, 16... Light source, 18... Developer, 19... Bias voltage change circuit, 20 ...Pre-transfer charger, 22...Transfer charger, 24...Paper, 30...Drive circuit, 32...Print signal generator, 44...Control circuit.

Claims (3)

[Claims] (1) A first charging means for uniformly charging the surface of the electrostatic latent image carrier, and an electrostatic latent image consisting of a plurality of potential levels on the surface of the electrostatic latent image carrier charged by the first charging means. one light source for forming an electrostatic latent image, a developing means for developing an electrostatic latent image formed by this light source by attaching a different color toner charged with a different polarity, and an electrostatic latent image carrier attached by this developing means. A second step charges the different color toners on the top to the same polarity.
A multi-color image forming apparatus comprising: a charging means; and a transfer means for transferring a different color toner image on an electrostatic latent image carrier charged to the same polarity by a second charging means to an image receiving material. (2) a first charging means for uniformly charging the surface of the electrostatic latent image carrier; and a first charging means for uniformly charging the surface of the electrostatic latent image carrier; a signal processing means for converting and outputting a signal distinguishable from the background; and a first color and a second color on the surface of the electrostatic latent image carrier charged by the first charging means based on the output of the signal processing means. and one light source for forming an electrostatic latent image with three potential levels corresponding to the background, and the electrostatic latent image formed by this light source is used to attach two colored toners charged with different polarities. a second charging means for charging the two color toners on the electrostatic latent image carrier attached by the developing means to the same polarity; A multi-color image forming apparatus comprising: a transfer means for transferring two-color toner images on an electrostatic latent image carrier to an image-receiving material. (3) The multi-color image forming apparatus according to claim (2), further comprising a background potential level control means for changing the potential level of the background.